#!/bin/bash
LIMIT=19  # 上限

echo
echo "Printing Numbers 1 through 20 (but not 3 and 11)."

a=0

while [ $a -le "$LIMIT" ]
do
 a=$(($a+1))
 if [ "$a" -eq 3 ] || [ "$a" -eq 11 ]  # Excludes 3 and 11.
 then
   continue      # 跳过本次循环剩下的语句.
 fi
 echo -n "$a "   # 在$a等于3和11的时候,这句将不会执行.
done 